1. Field of the Invention
The present invention relates to automated data storage libraries that manage the loading, unloading, and transfer of portable data storage media to/from media drives as well as data exchange between library hosts and media loaded in such drives. More particularly, the invention concerns a data storage library having a robotic media transport device and featuring multipurpose slots configured to receive (1) a media drive, operable to read and/or write data from/to media removably loaded into the media drive, (2) a command relay port, operable to convey command signals from a host to the robotic device, or (3) a module of various other types. The robotic device is programmed to recognize which type of module occupies each slot, or whether a slot is empty, and communicate with the occupant appropriately.
2. Description of the Related Art
One of the most popular mass storage systems today is the data storage xe2x80x9clibraryxe2x80x9d. Generally, a data storage library connotes a great number of commonly housed portable (xe2x80x9cremovablexe2x80x9d) data storage media, which are moved among various storage bins, import/export regions, and media drives by a robotic media transport device. These libraries have become popular for many reasons. First, the portable data storage media, usually magnetic tape or optical media, are typically quite inexpensive relative to other storage formats such as magnetic disk drives. Furthermore, libraries are easily expanded to accommodate more data, by simply adding more media items. Additionally, most libraries can be easily updated with new equipment. For example, a new media drive can be introduced to the library to supplement or replace the existing media drives.
A number of different companies manufacture such libraries today, each model demonstrating various different features and operating principles. One significant manufacturer of data storage libraries is International Business Machines Corp. (IBM). Although a number of different IBM libraries have widespread use and commercial success, IBM engineers are continually seeking to improve various aspects of their libraries.
One area of focus is cost reduction, and more particularly, cutting hardware costs by designing libraries that are easily reconfigurable and share components where possible. It is often difficult, however, to design components that perform multiple functions or that respond to plural master units. Frequently, this level of flexibility requires the addition of a cumbersome layer of coordinating or supervising software code, which can ultimately reduce the performance of other unrelated aspects of the library. For instance, developing software to enable multiple incompatible hosts to manage a shared inventory of media items can be prohibitively difficult or expensive in many situations.
In other cases, a shared component may need to include separate ports for different hosts, thus increasing the hardware cost of the shared component. Furthermore, some configurations experience incompatibility when multiple components share a bus or other feature, resulting in reduced or lost data availability. Thus, engineers are confronted with a number of difficult challenges in their quest to consolidate components or otherwise reduce hardware expenses in a data storage library. One approach that addresses the foregoing concerns is set forth in U.S. patent application Ser. No. 08/931,856, filed on Sep. 16, 1997 in the names of Basham et al. and entitled xe2x80x9cAUTOMATED DATA STORAGE LIBRARY WITH CONTROL PATH TO SHARED ROBOTIC DEVICE VIA MEDIA DRIVE,xe2x80x9d. The entirety of the foregoing patent is hereby incorporated herein by reference.
Basham et al. disclose a data storage library featuring a dual purpose data/control path between a host computer and a media drive. This path conveys control signals and data between the host and drive, and also conveys robotic control signals from the host to a robotic media transport device coupled to the drive. Although this approach provides various benefits, IBM engineers are seeking new ways to reduce library costs and improve the customer""s options for reconfiguring the library. In this regard, one area of possible consideration is developing a system that is sufficiently reconfigurable, yet avoids the need for the customer to incur the expense of purchasing special, dual purpose media drives capable of conveying robotic control signals in addition to the normal drive functions. From a marketing standpoint, a related problem is that customers that have already elected to build a library utilizing a conventional media drive model might dismiss the Basham et al. library because it requires at least one unique media drive type, namely a proprietary dual purpose media drive capable of conveying host commands to the library""s robotic media transport device in addition to the normal drive functions. Thus, further improvements are still sought to reduce costs and improve the flexibility of configuring data storage libraries.
Broadly, the present invention concerns a data storage library having a robotic media transport device and also featuring multipurpose slots each configured to receive an occupant such as a media drive (to read and/or write data from/to media removably loaded into the media drive) or a command relay port (to convey command signals from a host to the robotic media transport device). The invention additionally contemplates the insertion and use of other modules in the slots, such as dual function media drive/relay ports, switches, hubs, gateways, routers, network storage, Ethernet units, DASD, hosts, storage emulators, etc. The robotic media transport device is programmed to recognize which type of module (if any) occupies each slot, and to communicate with any occupant appropriately.
Cables, connectors, or other couplings are provided to automatically or manually electrically couple any media drive or command relay port (or other module) occupying the slot with the robotic media transport device, and optionally with a host if applicable. For each slot, the robotic device determines a state of each slot including the type of module occupying each slot, or whether the slot is empty. For each slot occupied by a command relay port, the robotic device receives media transport commands from a host through the command relay port, and carries out these commands to move the media items among specified media locations including media storage bins, media drives, etc. For each slot occupied by a media drive, the robotic device may exchange various configuration information, system management messages, or nothing at all.
As described above, then, one aspect of the invention concerns an apparatus such as a data storage library. The invention may also be implemented in a number of other forms. For example, the invention may be implemented to provide a method operable in a data storage library. In still another embodiment, the invention may be implemented to provide a signal-bearing medium tangibly embodying a program of machine-readable instructions executable by a digital data processing apparatus to operate in a data storage library as discussed herein. Another embodiment concerns logic circuitry having multiple interconnected electrically conductive elements configured to operate in a data storage library as discussed herein.
The invention affords its users with a number of distinct advantages. Significantly, this invention preserves the customer""s data storage library investment, since command relay ports can be upgraded to externally communicate using new and different host interconnects and/or protocols while preserving the same type of internal communications with the robotic device. Thus, by upgrading command relay ports as necessary, the customer can isolate the robotic device from changes in technical standards or technology itself. Changes to the library""s host interfaces therefore need not render the robotic device obsolete. The invention also offers an advantage in that the data storage library accommodates a variety of different slot occupants, and can be reconfigured as to the number and type of such occupants, number and type of host connections to the robotic device, and the like. In this regard, the invention is scalable, since the customer may increase (or decrease) the number of command relay ports at any time to accommodate a host being added (or removed); moreover, this benefit is possible without having to dedicate space in the library for any ports. Relatedly, the invention is flexible because any given slot may be housed with a command relay port or media drive (or other module), giving the advantage of increasing host connections, data access devices, or logical libraries within one library system.
Also, since the robotic media transport device communicates with separate hosts via separate command relay ports, and may be configured to partition the body of media items for non-overlapping host access, the invention avoids complicated host software that would otherwise be required to operate shared components. And, in the event multiple command relay ports are installed, the invention also offers the advantage of providing redundant paths to the robotic device, which may be useful when a desired path to the robotic device fails or is otherwise unavailable. Also, since the slots may house distinct and even incompatible command relay ports, the library of the invention is beneficial because it enables sharing of a single robotic media transport device and a common inventory of media items despite having a heterogeneous mix of otherwise incompatible hosts, application software and/or communication protocols.
As another advantage, having multiple, separate command relay ports corresponding to separate hosts simplifies partitioning of the media items in the library. Namely, the robotic media transport device may associate each command relay port with a different partition of media items, restricting all media transport commands arriving over a given command relay port to the corresponding partition. This simplifies host processing, since each host enjoys exclusive access to its own perceived xe2x80x9clibrary,xe2x80x9d although this xe2x80x9clibraryxe2x80x9d is actually a smaller partition of the entire body of media items. Further, partitioning helps preserve the security and integrity of the library by preventing different hosts from confusing each other by inconsistently using shared media items. As compared to the use of a completely separate library for each host, which would also preserve library security and integrity, partitioning reaps a certain economy of scale by sharing the library housing, shelves, robotic mechanism, and other common library infrastructure.
The invention also provides a number of other advantages and benefits, which should be apparent from the following description of the invention.